1. Field of the Invention
The invention lies in the field of semiconductor layer arrangements made according to the so-called LOCOS or isoplanar process.
2. Description of the Prior Art
The miniaturization of the field oxide structure has a limit placed on it by the length of the thick oxide bird's beak. Given the same field oxide thickness and mask layer, the minimum length is all the greater, the lower the oxidation temperature is set. The enlargement of the minimum field oxide width with decreasing temperature can be prevented when nitride is employed directly on silicon as a masking layer (Siemens Forschungs- und Entwicklungsbericht, Vol. 10 (1981), pages 357-361).
Nitrogen implantation and thermal nitridation (plasma enhanced) of the silicon wafer before generation of the pure silicon dioxide/nitride masking layer leads to a disappearance of the bird's beak given field oxide thicknesses up to 0.5 .mu.m, particularly given higher oxidation temperatures (.gtoreq.950.degree. C.). This technology is disclosed in IEEE Transactions on Electron Devices, Vol. ED-29, No. 4, pages 554-561.